From: ftp-bimas.cit.nih.gov Last mod: June 27, 1999
A new method of selecting loop breakers
Alejandro A. Schaffer
|*| Selecting loop breakers easily and automatically
Exercise 7 on pages 93--96 of Handbook of Human Genetic Linkage
by Ott and Terwilliger describes a complicated, interactive method
to break loops using the makeped program and the LOOPS program
LOOPS [Xie X, Ott J: Finding all loops in a pedigree.
Am J Hum Genet 1992; 51:A205].
As a result of innovations in FASTLINK 4.0P and FASTLINK 4.1P,
their method is now obsolete.
The new method is as follows:
1. When running your pre-makeped file through makeped, ALWAYS say
that the pedigrees have no loops, even if they do.
2. Put the post-makeped pedigree file in pedfile.dat.
3. Put the locus file in datafile.dat.
4. Run
unknown -l
Note that the flag is the letter 'l', not the number '1'.
This will produce a new output file called
lpedfile.dat
which has all the loops broken for you.
If your goal is to run an lcp-produced script
with pedigree file in pedin.dat and locus file in
datain.dat, you then
5. Copy lpedile.dat to pedin.dat
6 Copy the locus file to datain.dat
and run your script.
You will see diagnostic output showing that unknown is still trying
to find a better loop breaker set for you during the running of
the lcp-produced script. The reasons are as follows.
A. Your pedigree file may have dozens of loci while any specific
analysis may have only 2 or 3. The initial loop breaker set
selected by
unknown -l
attempts to be good for all loci, but may not be optimal for
any specific locus subset.
B. The method used during the main run uses a more precise
weight function to choose among the loop breaker possibilities
than does the preliminary run of
unknown -l